title: Parity and kidney cancer risk: evidence from epidemiologic studies.
abstract: BACKGROUND
  Observational studies have reported conflicting results between parity and kidney cancer risk. To our knowledge, a comprehensive and quantitative assessment of the association between parity and kidney cancer has not been reported. Thus, we conducted a systematic review and dose-response meta-analysis of published epidemiologic studies to summarize the evidence of this association.
  
  
  METHODS
  Relevant published studies of parity and kidney cancer were identified using MEDLINE (PubMed) database through end of June 2013. Two authors independently assessed eligibility and extracted data. Six prospective and eight case-control studies reported relative risk (RR) estimates and 95% confidence intervals (CI) of kidney cancer associated with parity or parity number. Fixed- or random-effects models were used to estimate summary relative risk.
  
  
  RESULTS
  The summary relative risk of kidney cancer for the parity versus nulliparous was 1.23 (95% CI, 1.10-1.36; Q = 12.41; P = 0.413; I(2) = 3.3%). In addition, significant association was also found for the highest versus lowest parity number, with summary RR = 1.36 (95% CI, 1.19-1.56; Q = 8.24; P = 0.766; I(2) = 0%). In the dose-response analysis, the summary per one live birth relative risk was 1.08 (95% CI: 1.05-1.10; Q = 9.34; P = 0.500; I(2) = 0%), also indicating the positive effect of parity on kidney cancer risk. No evidence of publication bias and significant heterogeneity between subgroups was detected by meta-regression analyses.
  
  
  CONCLUSIONS
  In summary, findings from this meta-analysis suggest that ever parity and higher parity number is significantly associated with increased risk of kidney cancer.
  
  
  CONCLUSIONS
  The present results suggest a positive association between parity and kidney cancer risk.
authors.affiliation: Authors' Affiliations: Department of Obstetrics and Gynecology, Shengjing Hospital, China Medical University, Shenyang; Department of Epidemiology; and State Key Laboratory of Oncogene and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Guan
authors.forename: Qi-Jun
authors.initials: QJ
authors.lastname: Wu
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Gong
mesh_terms: D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D015994:Incidence; D007680:Kidney Neoplasms / Q000453:epidemiology*; D010298:Parity; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology; D012307:Risk Factors